This invention is directed to novel additives to improve the low-temperature characteristics of liquid hydrocarbyl fuels, especially distillate fuels and to fuel compositions containing them.
Traditionally, the low-temperature properties of distillate fuels have been improved by the addition of kerosene, sometimes in very large amounts (5-70 wt %). The kerosene dilutes the wax in the fuel, i.e. lowers the overall weight fraction of wax, and thereby lowers the cloud point, filterability temperature, and pour point simultaneously. The additives of this invention effectively lower both the cloud point and CFPP of distillate fuel without any appreciable dilution of the wax component of the fuel.
Other additives known in the art have been used in lieu of kerosene to improve the low-temperature properties of distillate fuels. Many such additives are polymeric materials with pendant fatty hydrocarbon groups, and are usually derived from the free radical polymerization of unsaturated hydrocarbons (olefins, acrylates, fumarates, etc.). These additives are limited in their range of activity, however; most improve fuel properties by lowering the pour point and/or filterability temperature. These same additives have little or no effect on the cloud point of the fuel.
Applicants, to the best of their knowledge are unaware of any art that teaches or suggests the additive products disclosed herein. For example, U.S. Pat. No. 4,524,007 discloses the use of polycarboxylic mellitic anhydride acids, anhydrides such as pyromellitic anhydride (PMDA) reacted with ether capped alcohols to provide demulsifying additives for lubricants.
The additives of this invention are substantially different, however, both in terms of structure and function. The oligomeric and/or polymeric materials obtained via condensation reaction, e.g. the reaction of aminodiols with acids and/or anhydrides. In terms of activity, these additives effectively lower distillate fuel cloud point, thus providing improved low-temperature fuel properties, and offering a unique and useful advantage over known distillate fuel additives.